i40iw: Protect req_resource_num update

i40iw: Protect req_resource_num update

commit 44856be3e95c87f03e850ef4fdf8c0503c2dde18 upstream.

In i40iw_alloc_resource(), ensure that the update to
req_resource_num is protected by the lock.

Fixes: 8e06af711bf2 ("i40iw: add main, hdr, status")
Reported-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>